What Is GLP-1?

If you've seen the headlines about Ozempic, Wegovy, or Mounjaro, you've heard about GLP-1 medications — even if you didn't know what they were called. They're among the most discussed pharmaceutical developments in years. But the media coverage tends to oscillate between breathless enthusiasm and alarmed caution without explaining what these medications actually are and how they work.

This guide covers the basics clearly, without pharmaceutical marketing language and without catastrophizing. By the end you'll understand what GLP-1 means, how the medications work in your body, how semaglutide and tirzepatide differ, and what questions to ask a provider if you're considering this path.

What does GLP-1 stand for?

GLP-1 stands for glucagon-like peptide-1. It is a hormone your body naturally produces in the small intestine in response to eating. When you eat, your gut releases GLP-1, which travels through your bloodstream and does several things: it signals your pancreas to release insulin, it tells your stomach to slow down emptying, and it signals your brain to reduce appetite.

In other words, GLP-1 is part of the body's natural system for regulating blood sugar and telling you when you've had enough to eat. People with obesity or type 2 diabetes often have impaired GLP-1 signaling, which is part of why appetite regulation is harder for them than for people who don't face those conditions.

How do GLP-1 medications work?

GLP-1 receptor agonists are synthetic versions of the GLP-1 hormone designed to mimic its effects — but more potently and for much longer. While your natural GLP-1 breaks down within minutes, the medications are engineered to last for hours or days.

The result is a sustained reduction in appetite that most people experience as less hunger between meals, feeling full more quickly when eating, and fewer cravings for high-calorie foods. The stomach-slowing effect (delayed gastric emptying) also contributes — food stays in the stomach longer, extending the feeling of fullness after eating.

These aren't stimulants and they don't directly burn fat. They work by changing the hormonal signals that govern appetite and satiety. People on GLP-1 medications typically eat less because they feel less hungry, which produces weight loss over time.

Semaglutide vs. tirzepatide — what's the difference?

Semaglutide (brand names: Ozempic for diabetes, Wegovy for weight management) is a GLP-1 receptor agonist. It binds to and activates the GLP-1 receptor in the body.

Tirzepatide (brand names: Mounjaro for diabetes, Zepbound for weight management) is a dual-agonist. It activates both the GLP-1 receptor and the GIP receptor. GIP (glucose-dependent insulinotropic polypeptide) is another gut hormone that affects appetite and fat storage. Activating two receptors instead of one appears to produce greater average weight loss in clinical trials.

In the SURMOUNT-1 trial, tirzepatide produced average weight loss of up to 22.5% of body weight at the highest dose over 72 weeks. In the STEP-1 trial, semaglutide produced average weight loss of approximately 14.9% over 68 weeks. Both are meaningful. Individual results vary significantly based on starting weight, dose, adherence, diet, and activity level.

Brand-name vs. compounded — a critical distinction

Brand-name semaglutide and tirzepatide are FDA-approved and manufactured by Novo Nordisk and Eli Lilly respectively. Because demand has significantly outpaced supply since 2021, the FDA has declared shortages of these medications, which allows licensed compounding pharmacies to legally produce compounded versions containing the same active ingredients.

Most GLP-1 telehealth programs use compounded semaglutide or compounded tirzepatide because it is less expensive and more readily available than brand-name products. Compounded medications are not FDA-approved in the same way as brand-name drugs, and quality can vary between compounding pharmacies.

When evaluating a GLP-1 program, ask which compounding pharmacy fills your prescription and whether it holds PCAB (Pharmacy Compounding Accreditation Board) accreditation. This is one of the most meaningful quality indicators available.

Common side effects

The most common side effects of GLP-1 medications are gastrointestinal — nausea, vomiting, diarrhea, and constipation. These typically occur early in treatment and during dose increases, and they often improve as the body adjusts. Titrating up slowly (starting at a low dose and increasing gradually) significantly reduces the severity of these effects, which is one reason the titration protocol matters when comparing programs.

Less common but more serious potential effects include pancreatitis and gallbladder issues. GLP-1 medications carry an FDA boxed warning regarding a potential increased risk of thyroid tumors based on animal studies, though this has not been confirmed in human data. People with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2 should not use GLP-1 medications.

This is not a complete list of side effects or contraindications. A licensed healthcare provider who reviews your full medical history is the appropriate person to evaluate your individual risk profile before prescribing.

Is a GLP-1 program right for you?

That's genuinely a question for a licensed provider, not for a comparison site. What we can tell you is what the clinical guidance suggests about appropriate candidates.

GLP-1 medications for weight management are generally considered for adults with a BMI of 30 or higher, or a BMI of 27 or higher with at least one weight-related condition such as type 2 diabetes, high blood pressure, or high cholesterol. These are the criteria used in the clinical trials that established the medications' safety and effectiveness.

If you meet those criteria and want to explore your options, the next step is a telehealth consultation with a licensed provider who can evaluate your medical history and determine whether a GLP-1 program is appropriate for you. That's exactly what the programs we compare on this site offer.